Gas phase plasma technology has numerous applications in electronic manufacturing—in products ranging from semiconductor devices to optoelectronic components. Plasma processes are commonly utilized to modify the physical or material properties of a structure at some point in the manufacturing process. Contamination removal, surface activation, and etch processes are among some of the common applications for plasma processes.
Depending upon the specific requirements or limitations of a given manufacturing process, a wide variety of gases and materials may be utilized in the formation and application of a plasma. Consider, for example, a plasma etch process utilized in a semiconductor manufacturing process. Commonly, a feed or source gas is conducted through a flow tube to a reaction area. While moving through the flow tube, the reactivity of the source gas is increased by exposing the source gas to a microwave or radio frequency power source—creating a plasma. Given its extreme and volatile nature, such a process is usually operated within some sort of vacuum environment.
Commonly, such systems utilize quartz tubes. Conventionally, quartz tubes have been easy to manufacture. The extent to which quartz tubes have withstood the environmental stresses of plasma systems has varied, however. To a certain extent, exposure to a plasma process gradually degrades the structural integrity of a quartz tube.
Extended use in a system can cause the wall of a tube to wear thin and rupture. Newer manufacturing and plasma materials have further accelerated the degradation of the usable life of quartz tubes. For example, the introduction of CF4 into plasma systems can cause a chemical etching of the inside of a quartz tube—weakening the tube even faster than normal.
In addition to degradation of tube material, there are certain mechanical stressors in conventional plasma systems that damage or destroy conventional quartz plasma tubes. Conventional quartz tubes commonly comprise a single thickness tube having a flange portion at one end. That flange portion typically engages with some portion of the apparatus, while the un-flanged end of the tube is engaged with some sort of clamping mechanism to hold it in place—a compression ring fitting, for example.
As the system is pumped down to create a vacuum, the tube and its surrounding components are compressed together. If, however, there is any misalignment of the tube with respect to the components it engages, a bending moment or movement of the tube may result. This can cause a fracture or rupture of the tube, or unevenly expose the tube to a power source, further weakening or damaging the tube. In other instances, tube misalignment can cause some degree of melting in portions of the tube that are too close to an energy source (e.g., RF coil).
In addition to damage done to the tubes themselves, failures or faults in a tube can also do extensive damage to other components within a plasma system. For example, a rupture in a conventional quartz tube can result in arcing between the tube and an external RF coil. Aside from potentially ruining the plasma process, this can also cause damage to the RF coil—increasing system down time and repair expenses.
It appears that some conventional systems have attempted to address misalignment issues using supplemental mechanical apparatus. In some cases, support jigs or superstructures have been added to plasma systems to force a desired physical alignment of a plasma tube. Unfortunately, such measures add to the cost of the system, and introduce a number of reliability and maintenance variables to system operation.
As a result, there is a need for a system that provides plasma tubes that can withstand a wide variety of physical and environmental stressors within a plasma generation system, without relying upon supplemental support structures—providing efficient and reliable plasma processing in an easy and cost-effective manner.